Multiple myeloma (MM) is a common hematological malignancy. Autologous hematopoietic stem cell transplantation (auto-HSCT) can significantly improve the prognosis of patients with MM, but a variety of complications may occur after transplantation. Retroperitoneal fibrosis (RPF) is a rare cause of obstructive nephropathy. Because there are no specific symptoms at the time of onset and the course of the disease is often insidious, special laboratory and instrumental examination methods are usually needed to confirm the diagnosis. This article describes the clinical case of a 50-year-old female patient diagnosed with multiple myeloma. She developed postoperative acute kidney injury (AKI) more than 20 days after transplantation and was subsequently diagnosed with retroperitoneal fibrosis. After multidisciplinary collaboration, early transurethral vesicoureteral stent placement was performed, the obstruction was relieved, and her renal function returned to normal. Reports of retroperitoneal fibrosis after multiple myeloma transplantation are relatively rare. This case report advances our understanding of these 2 diseases, and the correlation between MM and RPF warrants further exploration.Copyright © 2024. Published by Elsevier Inc.